The technical field is that of solid-state power controllers and, more particularly, the control of such controllers.
Solid-state power controllers (SSPCs) are elements that make it possible to manage the distribution of electrical power to aircraft loads via lines conveying the electrical power and the protection of these lines. They are composed of a control portion and a power portion, comprising switching elements based on semiconductor components. The term “aircraft loads” is understood to mean on-board items of equipment that consume electrical power. They are generally installed on circuit boards.
These circuit boards, generally called switchboards or SSPC boards, comprise at least one power pathway controlled by a solid-state power controller, or SSPC controller. A circuit board is generally composed of multiple power pathways per SSPC board. Each power pathway comprises a power switch, which closes or opens the connection between a power source and a load, and which is composed of one or more switches. The switches may be of JFET (junction gate field-effect transistor), MOSFET (metal-oxide-semiconductor field-effect transistor), IGBT (insulated-gate bipolar transistor) or bipolar transistor type. These switches may be produced in various materials, such as Si, SiC or GaN. This power switch is combined with a control member, the control portion of the SSPC controller, in order to control these switches in complete safety.
A switching pathway is said to be protected since the SSPC controller monitors the amplitude of the currents and voltages passing through the pathway according to nominal values. The SSPC controller is capable of interrupting the electrical power supply through the pathway in the event that one or more of these values is exceeded by controlling the switching of the power switch.
Switchboards generally form part of the on-board electrical distribution equipment of aircraft. Due to the average power transmitted by the power pathways involved, these protection boards form part of the secondary distribution equipment.
It must be possible to regulate the closing time of a switching pathway in a controlled manner, in order to limit the inrush current during closing phases with a capacitive load. This means controlling the power switches such that the impedance seen from the source is essentially resistive and varies gradually in order to allow a gradual rise in the output voltage. Such behaviour of the output voltage is hereinafter referred to as “soft-start” control.
The opening time of the power pathway must, however, be fast enough to prevent damage to the power pathway in the event of a short circuit.
FIG. 1 illustrates an architecture of the prior art with one power supply and one control means per power pathway, the power supply and the signal arising from the control means being electrically isolated. Two power pathways 1a, 1b included in an SSPC board 2 may be seen. Each power pathway 1a, 1b comprises a power line 6a, 6b connected in series with a power switch 7a, 7b and a measurement resistor 8a, 8b. Each power switch 7a, 7b is controlled by a control member 9a, 9b. 
Each power pathway 1a, 1b comprises a control means 10a, 10b connected to the control member 9a, 9b and to the measurement resistor 8a, 8b via isolation means 3a, 3b, 4a, 4b, 5a, 5b. The isolation means may be optocouplers, magnetic couplers or any other information transfer system with galvanic isolation. It should be noted that the isolation means 5a, 5b connected to the measurement resistor 8a, 8b and the corresponding measurement resistor may be replaced by a Hall effect sensor which allows both the current flowing through the power line 6a, 6b to be measured and the control means 10a, 10b to be galvanically isolated from the corresponding power line 6a, 6b. 
The means for isolating the power supply 3a, 3b are for example transformers allowing galvanic isolation.
Each control means 10a, 10b comprises logic elements allowing a command to be sent to the control member 9a, 9b as long as no overly high current fault has been measured. In such a case, the command intended for the control member 9a, 9b is overridden and replaced by an opening command the purpose of which is to protect the aircraft loads and the wiring connected to the power line.
FIG. 1 illustrates one example of such a control means 10a, 10b, comprising a comparison means 11a, 11b connected to the set input of a fault memorization system referenced 12a, 12b. The output of the latch is connected to an AND logic gate 13a, 13b which additionally receives the control signal to be transmitted to the control member 9a, 9b. 
The means 11a, 11b for comparing a measurement of the current flowing through the corresponding power pathway with a memorized reference value is capable of transmitting, as output, a Boolean value on the basis of the comparison.
When the transmitted signal corresponds to an exceedance of the memorized reference value, the latch 12a, 12b is locked so as to maintain the transmission of this signal. The signal corresponding to an exceedance of the memorized reference value then blocks the control signal received at input of the logic gate 13a, 13b. This situation persists regardless of the value subsequently transmitted by the comparison means 11a, 11b and until an appropriate signal is received on the reset input of the latch 12a, 12b. 
In the case of the architecture illustrated by FIG. 1, certain drawbacks are apparent.
The greater the number of protected pathways, the larger the area occupied by the isolated power supplies. Specifically, in this architecture, one protected pathway switched by one control member corresponds to the use of one isolated power supply and one isolated command. The multiplication of components required to control multiple protected pathways is accompanied by an increase in costs, in dissipated power and in the area required for implementation, at the expense of useful area for power switches.
The greater the number of switching pathways, the shorter the mean time before failure (MTBF) of the SSPC board. Specifically, the isolated power supply and the galvanic isolation members play a very large role in the MTBF value of a circuit board, more particularly of an SSPC board.
The presence of multiple switched-mode power supplies leads to electromagnetic compatibility issues which are difficult to solve without filtering. The multiplication of pathways on one and the same board amplifies these interferences and the area occupied by the various filters becomes non-negligible.
Achieving soft-start control using this architecture requires the addition of an isolation means and other elements which in turn increase the space occupied.